Drying and heating oven



Unt. 2, M69 @-1. s. ARNOLD ET AL @473,792

DRYING AND HEATING OVEN 2 Sheets-Sheet 2 Filed Dec. '7, 1967 Z WMW N Ef W42? m5 60 und 3,473,792 DRY ING AND EATING OVEN Henry S. Arnold, 2024 Arnold Road, Birmingham, Ala.

35216, and .loe W. Green, 1040 Drexel Drive, Birmingham, Ala. 35209 Filed Dec. 7, 1967, Ser. No. 688,884 Int. Cl. F271) 9/14; F23! 9/04 ILS. Cl. 263-6 5 Claims ABSTRACT OF II-IE DISCLOSURE :BACKGROUND OF THE INVENTION This invention relates to a finish drying and heating oven and more particularly to an oven for drying or curing finishes such as lacquers, enamels, varnishes, resin coatings and the like on articles such as furniture, 'building panels, doors and the like.

Heretofore in the art to which our invention relates, difficulties have been encountered in drying and curing finish coatings on articles, such as articles of furniture due to the fact that it has required from twenty `minutes to more than an hour to heat such finishes. This not only increases the space and equipment required to heat the articles but also delays the packaging of the articles. Also, it has been the general practice to employ an open llame in the furnace whereby certain areas of the furnace are heated at higher temperatures than other areas thereof and at the same time it is necessary to provide re brick in the high temperature areas of the oven.

BRIEF SUMMARY OF INVENTION In accordance with our invention, we apply a relatively high heat to the surface of the article being dried or cured and provide for rapid heat transfer to the surface of the article with heat penetration held at a minimum due to the short time that heat is applied, thus reducing the time and etiort required to dry the articles and at the same time reducing the packaging time since the articles are at a safe temperature to be packaged soon after leaving the oven. We employ a gas discharge conduit which communicates at one end with a gas heating unit. One end of an elongated closed housing surrounds the discharge conduit and is spaced therefrom for receiving air under positive pressure which is introduced between the housing and the discharge conduit in a direction generally perpendicular to the direction of travel of the heated gas through the discharge conduit.

Apparatus embodying features of our invention is illustrated in the accompanying drawings, forming a part of this application, in which:

FIG. l is an end elevational view of the apparatus, partly broken away and in section;

FIG. 2 is a top plan view of the apparatus shown in FIG. 1;

FIG. 3 is a vertical sectional view taken generally along the line 3-43 of FIG. l;

FIG. 4 is an enlarged, fragmental View taken generally along the line 4-4 of FIG. l; and,

FIG. 5 is a view taken generally along the line 5-5 of FIG. 4.

nited States Patent O ice Referring now to the drawings for a better understanding of our invention, we show an oven 10 having a top wall 11 and vertical side walls 12, 13, 14 and 15, as shown in FIG. 2. Doorways or openings 16 are provided in the vertical walls 12 and 14 for passing the articles having coatings thereon to be dried or cured, one such article being indicated in dotted lines as at 17 in FIGS. l and 3. The articles 17 are supported by movable platforms 18 mounted on supporting wheels 19 which travel in suitable guideways 21, as shown in FIG. 1. Each conveyor platform 18 is moved longitudinally of the guideways 21 through the oven 10 by an endless drive chain 22 having upstanding detents 23 at longitudinally spaced intervals for engaging depending member 24 carried by the conveyor platforms 18. The chain 22 passes around suitable drive sprockets `26 adjacent the ends thereof and is supported intermediate its ends by suitable means, such as idler sprockets 27.

Mounted within the upper portion of the oven 10 and projecting outwardly through a suitable opening in the vertical wall 12 is an elongated, cylindrical housing 28. Secured to the end of the elongated housing 28 projecting outwardly of the oven 10, by suitable means such as stud bolts 29 and nuts 31, is an annular plate member 32 having a centrally disposed opening 33 therein for receiving the end of a conical sleeve 34 of a heating unit indicated generally at 36. Surrounding the conical sleeve 34 is a cylindrical housing 37 which is secured at one end to the annular plate 32. The other end of the cylindrical housing 37 is closed by a head plate 38 having a centrally disposed opening 39 therein for threadedly receiving the end of a conduit 41 which supplies a combustible gas to the heating unit. A conventional type gas pilot is provided for the heating unit 36 which is ignited by a high voltage ignition system indicated at 42. A built-in safety device is associated with the gas pilot whereby the system is made inoperable and the gas supply is cut olf when the flame fails. The safety device is in the form of arne rods 43 which are in the pilot dame constantly whereby upon failure of the ilame the flame sensor activates suitable mechanism to cut off the gas supply. The supply of gas to the heating unit 36 is controlled by a valve 44 and a pressure gauge 46 indicates constantly the pressure of the fuel delivered to the heating unit.

The sleeve 34 is provided with a plurality of openings 47 therethrough for delivering air for combustion. The air is supplied to the housing 37 by a conduit 48 which communicates with a larger conduit 49 which in turn communicates with the discharge end 51 of an air blower indicated generally at 52. The conduit 49 is perpendicular to and communicates with the adjacent side of the elongated cylindrical housing 28, as shown in FIG. 5 whereby one side of the conduit 49 is tangent to one side of the cylindrical conduit 28.

Mounted Within the elongated housing 28 adjacent the annular plate 32 and surrounding the discharge opening of the sleeve 34 is a discharge conduit 53 which is spaced from the inner surface of the elongated housing 28, as shown in FIGS. 4 and 5, to define an annular passageway 54 between the discharge conduit 53 and the cylindrical housing 28 whereby upon introducing the air through conduit 49, the air passes over one side of the discharge conduit 53 and then moves around the same in a spiral-like manner. As shown in FIG. 4, the discharge conduit 53 terminates within the elognated cylindrical housing 28 and intermediate the ends thereof whereby the products of combustion discharged from the discharge conduit 53 are encased by the spirally moving air discharged from the annular passageway 54, thus thoroughly mixing the air with the products of combustion to provide a uniformly heated gas within the closed housing 28. The

centrifugal force imparted to the air within the annular passageway 54 causes an axial force to be imparted to the circulating gas whereupon it is discharged from the annular chamber I54 in a spiral-like manner around the products of combustion discharged from the discharge conduit 53. The air introduced through conduit 49 is under a positive pressure relative to the pressure within the housing 28 to thus impart centrifugal force to the gases as it moves around the discharge conduit 53 and at the same time there is no danger of a flash-back. Preferably, the air is discharged from the blower 52 at a positive pressure of from one-half pound to four pounds pressure per square inch whereby the burner is fired under a positive pressure. That is, the air discharged from the blower 52 passes through conduits 48 and 49 whereby the necessary air to support combustion is delivered into the housing 37 whereas the remainder of the air is delivered through conduit 49 to the closed housing 28.

The end of the elongated cylindrical housing 28 opposite the end thereof connected to the heating unit 36 communicates with a transverse, laterally extending conduit 56 which in turn communicates at opposite ends with lateral conduits 57 and 58, as shown in FIG. 2. The discharge ends of the conduits 57 and 58 communicate with longitudinally extending conduits 59 and 61, respectively, which extend generally parallel to the side walls 13 and 15. Communicating with the conduits 59 and 61 and depending therefrom are a plurality of vertical conduits 62. The depending conduits 62 carried by the horizontal conduit 59 are connected to and communicated with inwardly extending, horizontal conduits 63. In like manner, the depending conduits 62 carried by the horizontal conduit 61 are connected to and communicate with inwardly extending, horizontal conduits 64. As shown in FIG. l, the conduits 63 and 64 are at an elevation slightly above the passageways 16 through the oven 10. A plurality of longitudinally spaced discharge nozzles 66 communicate with the inner surfaces of the vertical conduits 62 and the horizontal conduits 63 and 64 whereby the heated gases are discharged at a high velocity onto the article 17 having the surface to be dried or cured.

From the foregoing description, the operation of our improved drying apparatus will be readily understood. Before tiring the heating unit 36, air is circulated through the oven for approximately two minutes to purge all combustible gases from the oven. After purging the apparatus, the pilot is ignited by the ignition system 42. The valve 44 is then turned on whereby a predetermined flow of gas is delivered to the heating unit in a manner well understood in the art to which our invention relates. Air for combustion is supplied through the branch conduit 48 while the remainder of the air delivered under positive pressure from air blower 52 is delivered to the housing 28 in a direction generally perpendicular to the direction of movement of the gases or products of combustion through the discharge conduit 53. As the air is delivered around the discharge conduit 53, it moves in a spiral path whereby the centrifugal force of the moving stream of gas around the discharge conduit 53 causes an axial force to be imparted to the air whereupon it is discharged from the annular space 54 in a spiral which encases the products of combustion discharged from the discharge conduit 53. This movement of the air and the products of combustion causes a thorough and uniform mixing of the air with the heated products of combustion. Also, as the air circulates about the discharge conduit 53, it is heated prior to being mixed with the products of combustion. The thoroughly mixed gases are delivered to the discharge end of the housing 28 at a predetermined temperature whereupon the heated gases then pass laterally through the conduits 57 and 58 to the conduits 62, 63 and 64. The heating gases are then discharged at a high velocity through the discharge nozzles 66 onto the article 17 carrying the surface to be dried or cured.

All of the air delivered through the discharge nozzles 66 is at substantially the same temperature whereby there is no overheating of any portion of the article 17. The high velocity air discharged through the nozzles 66, in addition to the turbulence created by the air, moves away all stagnant films of stationary air which might surround the article 17, thus bringing about a high transfer of heat to the surface to be heated. The ilow of air through the conduits 48 and 49 is controlled by valves 67 and 68 whereby the required air is delivered for combustion and for delivery to the elongated housing 28. i

The burner unit is regulated whereby the temperature in the heating unit is approximately l,200 F. or higher. With the temperature in the heating unit 36 at 1,200 F.. the temperature of the heating gases discharged iby the nozzles 66 ranges from approximately 300 F. to 600 F. The temperature of the portion of the oven'which surrounds the article to be dried then ranges from approximately 200 F. to 400 F. Accordingly, the heated gas is delivered at a temperature whereby it dries only the surfaces which are required to be heated. Due to the rapid heat transfer and the high temperatures employed, articles, such as articles of furniture,'can be dried within two minutes or less.

From the foregoing, it will be seen that we have devised an improved drying and heating oven which is particularly adapted for rapidly drying or curing articles of furniture and the like. By providing for a rapid heat transfer of the high temperature gases, together with the short time that the article is exposed to the heat, there is substantially no heat penetration of the article and at the same time the work product cools quickly to a temperature ranging from F. to 110 F. in approximately one to three minutes whereby the article may be packaged immediately without any damage to the coated surface. This is especially desirable where thermoplastic coatings are applied to the articles to be dried. By providing a compact, isolated heating unit which is positioned outwardly of the oven, together with means providing for uniform temperature of the gases discharged from all of the high velocity nozzles, there is no open flame within the oven, whereby we not only provide a uniformly heated gas at all of the discharge nozzles but also eliminate the necessity of constructing the oven of rire brick or other refractory materials to withstand extremely high temperatures.

While we have Shown our invention in but one form. it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What we claim is:

1. In a finish drying and heating oven having means for passing an article to be heated therethrough and means discharging heated gas onto said article, the improvement which comprises:

(a) a heating unit disposed to heat a gas and having a discharge passageway discharging heated gas therefrom,

(b) discharge conduit having a curved outer surface and communicating at one end with the gas discharge passageway of said heating unit,

(c) an elongated closed, cylindrical housing having one end thereof surrounding and spaced from said discharge conduit with the discharge end of said discharge conduit terminating within said housing and intermediate the ends thereof,

(d) means communicating the other end of said elongated housing with said means discharging heated gas into said article, and

(e) an inlet conduit introducing air under positive pressure between said elongatedcylindrical housing and said discharge conduit with one side of said inlet conduit being tangent to one side of said elongated cylindrical housing and generally perpendicular to the direction of travel of heated gas through said elongated cylindrical housing to heat said air and cause said air travel in a spiral-like path so that the air is mixed uniformly with the heated gas upon discharge of the heated gas from said discharge conduit into said housing.

2. In a nish drying and heating oven as defined in claim 1 in which the heating unit is a gas fired burner having means supplying air for combustion with the products of combustion passing out said discharge passageway into said discharge conduit as said heated gas.

3. In a finish drying and heating oven as defined in claim 1 in which said other end of said elongated housing communicates with laterally extending conduits which communicate with depending branch conduits having inwardly disposed discharge outlets for discharging heated gas onto said article.

4. In a nish drying and heating oven as dened in claim 3 in which inwardly extending branch conduits References Cited UNITED STATES PATENTS 2,110,209 3/1938 Engels. 2,391,339 12/1945 Pearson 263-6 3,208,740 9/1965 Nesbitt et al. 263--6 JOHN I. CAMBY, Primary Examiner U.S. Cl. X.R. 263-19 

